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Old 04-22-2015, 03:12 PM   #51 (permalink)
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If you go faster without the fairing, is it really an aerodynamic improvement? Maybe I'm missing something.

35 on a faired TT bike sounds more accurate. I don't think I'd like doing that kind of speed on a bike on the street anyway, with pinch flats and all. I'd definitely be running tubeless tires 2" wide or more for peace of mind and comfort. I wouldn't trust most recreational/occasional riders to be zipping around over 15 mph anyway, since no one really teaches kids or adults in this country how to ride safely.

You've obviously got quite a bit of experience in the motorized bicycle arena, and I stay out of that. What I can say is that a Michigan officer who shall remain nameless admitted that the likelihood of getting pulled over on a bicycle, even for running a red, is very small due to legal grey area and the difficulty of prosecution. I still try to be respectful to other road users and the law, but sometimes it's safer to bend the rules a bit. I think there is some understanding from law enforcement, but it's not entirely consistent so, of course, bend rules at your own risk .

I imagine that if you are riding an e-bike respectfully there wouldn't be much of a problem. People often ask my friend with the Pugsley and frame bag where the motor is. He points at his legs. I take this to mean that most people have a positive view of e-bikes, or are at least curious.

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Old 04-22-2015, 03:26 PM   #52 (permalink)
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Quote:
Originally Posted by Sven7 View Post
If you go faster without the fairing, is it really an aerodynamic improvement? Maybe I'm missing something.
Cd improvement + A increase = CdA loss.
Aerodynamic improvement, yes. Utility improvement, no.
But it's a step forward, working and learning.
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Old 04-22-2015, 03:58 PM   #53 (permalink)
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At this point my front fairing by itself is mostly good for weather protection. It is the first step in a full body system. It is light, very easy to make, and is very stable in high winds. What started me going was the now famous article in Scientific American Dec. 1983 (see zzipper.com). Compare the numbers of an aero tuck racer to the Easy Racer, they are very close. What we easily could see is a combination of the Oscar Egg Rocket tail and the Zzipper style front bubble attached to the head tube.

Getting on and off is a real issue. Moving the tail or a side panel is needed for access.

I expect to see more on handle bar water bottles and aero bottles mounted to the seat tube between the knees. Consider mounting the water bottles behind the seat horizontally so they can be used without raising the shoulders as much.

Based in the work done by Trek for the Speed Concept Kammtail Virtual Foil I will try adding some foam strips to the round tubes of my steel test frame.
Since I cannot afford blade spokes yet, I may try using some weed eater string and electrical tape to streamline the spokes in addition to partial front wheel covers.

As for tires I can see wider tubeless semi slick tires given the conditions of roads these days. Maxxis Hookworms have been joined by similar products.

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Old 04-22-2015, 04:25 PM   #54 (permalink)
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Ah, gotcha. A good place to start, no doubt.

I wonder if, instead of mucking about with spoke shape, one could develop a special hub brake specific rim design that had air trips to reduce the drag of spokes. Surely this would be hard to pull off, but maybe useful. Maybe the tires themselves could have trips. Maybe a special wheel cover could be developed that would have low Cd from the front, say at a 10 degree yaw or less, but would allow side winds to pass through. I'm imagining a louver cross section revolved in the Y axis.

Also, shouldn't this be in the Alt Transport forum?
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Old 04-22-2015, 10:14 PM   #55 (permalink)
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If it is bicycle specific I suppose it would. Wheel aerodynamics may have application to motorcycles too. A sketch would help us grasp the concept better.
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Old 04-23-2015, 11:32 PM   #56 (permalink)
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Remember that zigzag tape for glider planes?

I was wondering if putting something similar to that around the edge of the rim would do anything productive. Maybe it would create enough turbulence that the spokes could slice through the air more easily. You couldn't run rim brakes on it, but drums drag less anyway.

As far as the wheel design, I'm just thinking out loud at this point, but maybe something like this, but with spaces between the rings:



That way, maybe air would flow across it from the front, but side winds wouldn't catch it as much as a solid disc.
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Old 04-25-2015, 09:39 PM   #57 (permalink)
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Perhaps some form of louver on the front half of a shell.
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Old 05-07-2015, 12:36 PM   #58 (permalink)
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Probably from all the metall hardware...
Maybe that's the shipping weight they want to charge you?
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Old 05-07-2015, 01:02 PM   #59 (permalink)
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As a long time cyclist, most of this thread makes my head hurt. I know you all mean well but there is actually a cycling industry out there that has spent years, a lot of money and effort trying to tackle these issues.

Fairings are all good for the track or closed course but IRL (in real life), with hills, cross winds, storing the bike both at home and work, they are a heck of a lot of work with few benefits. A lot of the fairings and super-aero designs pictured here are useless on public roads with motor vehicle traffic.

The diamond frame bike has been around for 120 yrs. It has been studied, dissected, etc for a long time by people who spend their lives on bikes. I'm not saying that new things can't happen but a lot of what's been discussed in this thread has been tried. Many times. For years and years. There's a reason bikes still look like they do.

Yes, I'm aware of how the UCI limits technological improvement but even in ultramarathon cycling where participants are free to use conventional bikes or recumbents, very often, the conventional bike (think more like time trial/triathlon) bike is chosen because not only of aerodynamics but ergonomics.

At commuting speeds, rolling resistance can be as big a factor - skinny tires at high pressures isn't where it's at anymore. Check out Jan Heine's research on his website janheine.wordpress.com/

Most pros are moving to at least 25mm tires and wider rims. Enthusiasts are using from 25mm to as wide as 42mm fast rolling tires.True aero wheels cost upwards of $2000 so trying to plink some improvements off of wheels on a $300 bike seem unlikely. Aero wheels have their drawbacks in windy conditions, not to mention most are made of carbon fiber so require either special brake pads or disc brakes for proper braking (and typically very expensive tubular tires) which again bumps up the price tag.

Trying to fair tubing is also pretty meaningless at commuter speeds since most of the aero drag is from the rider and wheels. Also, what seems intuitive often isn't. Many bikes are actually more aero with a water bottle on the downtube since it pushes air around the legs and back wheel.

The most meaningful gains (within a reasonable budget) are going to be by
a) aero rider position - tri/tt bars in proper position so your back is flat as practical. Mounting aero bars way high on the flat bars of a commuter hybrid is not what I'm talking about.
b) low rolling resistance tires - fatter tires are also less prone to flatting. Spending time and money on making a fairing and then using heavy, stiff "commuting" tires is like taking one step forward and two back
c) more aero front wheel. Low spoke 50mm plus depth. But this alone is probably double the budget of the bike a lot of people in this thread are talking about.
d)f you want a fairing on the cheap, get a good proper handlebar bag to carry your work clothes in. Not that expensive, a heck of a lot more functional than sheets of chloroplast.
e) consider a better used bike.

Lastly, a 20km commute can be done by a fit cyclist in 35-50 min. A high level competitive cyclist, in as little as half hour. It may be that your best gains in time would be tuning the "motor" rather than the bike.
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Old 05-07-2015, 01:43 PM   #60 (permalink)
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For really practical aerodynamic cycling go velomobile

Velomobiles are the most practical solutions for aerodynamic cycling.
Providing weather protection, safety and high speeds.
Velomobiel.nl - Welkom or Velomobiles - bluevelo - Your velomobile source in North America

Greetings, Theo

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